The present invention concerns an electronic device for generating and displaying an item of information.
A device of the aforementioned type essentially includes an electronic unit intended to provide an item of information, a display cell connected to the electronic unit for displaying the information, and an electric power source powering the electronic unit.
A device of this type may constitute, for example, an electronic timepiece with a digital or pseudo-analogue display. In this case, the electronic unit includes a time base circuit formed by an oscillator and a frequency divider, and counters which supply time-related information in response to signals provided by the time base circuit. The display cell is then arranged so as to display this time-related information which generally include at least the hour and minute of the current time. Very often the electronic unit and the display cell are arranged so that the second of the current time is also displayed, as well as other information such as, for example, the date, the day of the week, a measured time or an alarm time.
It will be evident upon reading the following description that the present invention is not limited to the case wherein the device is a timepiece, but that it can be adapted without any difficulty to any case wherein an item of information is generated by an electronic unit is to be displayed by a display cell.
Devices of this type which are known to this date generally include a rigid case, made of metal or plastic, in which are mounted the display cell, the electronic unit and the electric power source which is generally a battery. These elements are joined mechanically by a frame housed in the case, and they are electrically connected by connecting elements.
The case is generally closed by a back cover and a crystal through which the display cell is visible. Finally, manual control members such as, for example, pushbuttons, are often mounted on the case to allow various functions of the device to be controlled, such as the time setting function if the device is a timepiece.
Despite all the simplifications which have been made to the construction and manufacture of such devices, they are still quite complicated and thus are not able to be manufactured at a very low price. Further, the known devices are generally fragile and not water resistant, unless special measures are taken. These special measures of course increase the cost price of these devices.
Finally, these known devices are relatively heavy, in particular when their case is made of metal, and they have a substantial thickness.
In order to overcome these drawbacks, the Applicant has already proposed, in European Patent No. EP 0 138 098, a device of the type defined hereinbefore which is both inexpensive, of small thickness and flexible. This device includes three stacked flexible elements, namely an electronic unit for generating an item of information, a display cell for displaying this item of information, and an electric power source for powering the electronic unit. These three elements are mechanically connected and electrically connected to each other respectively by insulating adhesive materials and conductive adhesive materials.
The display cell is a liquid crystal cell which includes, in a conventional manner, two plates which delimit it and surround the liquid crystal layer. These two plates are formed by thin films of plastic material, for example a polyester or another polymer. Consequently, the cell is very thin, and it has a certain flexibility, which allows it to be deformed without being damaged and without ceasing to operate. Such a cell may have a total thickness of approximately 0.2 mm.
The electric power source is formed by a flat battery which includes a positive plate made of stainless steel, a negative plate made of zinc and an electrolyte, for example zinc perchlorate, contained in a porous separator arranged between the two plates. The plates and the electrolyte of this battery are arranged between two thin sheets of plastic material or cardboard which are welded or bonded to each other at their periphery. As all the components of the battery are very thin, the battery is also very thin. It may have a thickness of less than 1 mm. Such a battery has a certain flexibility and can be deformed without ceasing to operate.
Finally, the electronic unit includes a printed circuit including a flexible insulating substrate on which are deposited conductive paths. The electronic unit further includes an integrated circuit and a piezoelectric resonator. The integrated circuit may be arranged so as to perform, for example, time measuring functions. The electronic unit is very thin. The substrate has a thickness of 0.2 to 0.3 mm, and the integrated circuit and the resonator have thicknesses of approximately 1.5 mm. Since the substrate is flexible, so is the electronic unit.
The display cell is applied against the top face of the electronic unit, and the electric power source is applied against the bottom face of the electronic unit. These three elements are mechanically connected and electrically connected to each other respectively by insulating and conductive adhesive materials. The device thus formed is very thin. As all the elements are flexible and the layers of adhesive are extremely thin, the device is itself flexible and can be deformed without ceasing to operate. One may, for example, give this device the general shape of a wristband and provide, at the ends thereof, clasp means. As a result of the flexibility of the sheets of plastic material and/or cardboard which form this device, it may be worn like a conventional wristwatch.
A portable device including a flexible display cell and a wristband which forms the body of the device is also known from International Patent Application No. WO 99/67702. The wristband allows the device to be secured for example around a person""s wrist. The portable device includes light flexible elements which allow it to match the shape of a given contour and to have a flat profile. The device can undergo the deformations to which a watch, for example, is subjected during normal physical activity, without being damaged. A clasp system made of a flexible polymer material is overmoulded onto the wristband.
The portable device may present information by means of the flexible display cell and a thin flexible piezoelectric loudspeaker. It may receive information via data input keys. The piezoelectric loudspeaker/microphone also allows the device to receive acoustic data. The portable device can communicate with external devices such as a computer or a smartcard reader via a communication element. This communication element may be an inductive loop deposited by screen printing inside the body of the device. The device may include an electric power source such as a flat lithium battery.
More precisely, the portable device includes top and bottom protective layers and spacers. The display cell is coated with a transparent material such as PVC. By molding or machining, the protective layers are given the necessary shape for receiving the internal components. These internal components include an integrated circuit mounted on a flexible printed circuit. The integrated circuit may include a microprocessor. The flexible display cell can be made using different materials. According to one embodiment, transparent electrodes are deposited on the inner faces of the top and bottom protective layers. The electrodes are shaped so as to provide a dot-matrix display or digit display. The display cell is formed of a liquid crystal display film which is a bi-stable or multi-stable material maintaining the displayed image even when the electric power supply is cut.
The microprocessor of the integrated circuit activates a control circuit which supplies the voltages necessary to activate and deactivate the pixels of the display cell. The electric power source arranged inside the portable device or an external power source (for example a smartcard reader) supplies the power necessary for the microprocessor and other elements to operate. The portable device can receive control pulses via data input keys. These keys which are dome-shaped, are laminated between the inner and outer protective layers of the portable device. Regions located directly below the data input keys are laminated inside with a rigid material to increase the reliability of said keys and to improve the reaction to the touch.
The devices of the type described hereinbefore have the particular advantage of being both flexible and of small thickness. Their main drawback lies however in the fact that certain of the components which form them are very fragile. This is true in particular for the integrated circuits which include, in a conventional manner, a silicon plate in which are formed the various electronic components necessary for performing the desired electronic function or functions. These silicon plates are coated with a protective layer generally made of glass. When a device of the aforementioned type constitutes, for example, an electronic timepiece, it further includes a quartz resonator element encapsulated in a ceramic or glass case. These various components are thus rigid and liable to be damaged or to cease operating when the device to which they are fitted is deformed to be able, for example, to be secured to a user""s wrist. The electric connections which connect between them the battery, the integrated circuit, the display cell and the quartz resonator in the event that the device is a timepiece, are also extremely fragile and are liable not to withstand the deformations to which a watch, for example, is subjected during normal physical activity.
The main object of the present invention is thus to overcome the drawbacks of the aforementioned prior art in addition to others by providing an electronic device of the type defined above which is both inexpensive, light, water resistant and especially not fragile.
The present invention thus concerns a device for generating and displaying an item of information including a flexible body which can, for example, be given the shape of a wristband to be able to be secured to a user""s wrist, an electronic unit for generating the information, a display cell for displaying said information, and an electric power source for supplying the electronic unit, characterised in that the flexible body has, at at least one location on its length, an overthickness of material forming a rigid receptacle in the inner cavity of which is arranged said electronic unit.
As a result of these features, the present invention provides an electronic device which is formed solely of a flexible body which can be given, for example, the shape of a wristband which is thicker and more rigid at its middle and flexible and thin towards its ends. Such a flexible body thus fulfils the two conventional functions of a wristwatch which are the protection of the most fragile components and the securing of the watch around its user""s wrist. Indeed, when the device according to the invention constitutes an electronic timepiece, the fragile electronic components such as the integrated circuit, the quartz resonator element or even the battery which form it are housed in the thick portion of the flexible body which they contribute to making more rigid. These components are thus sheltered from dust, water or humidity, and can withstand the mechanical stress to which the flexible body is subjected when it is deformed to be able to fit a given profile without being damaged or ceasing to operate. Likewise, the problem of the electric connections which connect between them the components described above is also resolved insofar as these components and the conductive paths which connect them are arranged in the rigid volume of the flexible body. A reliable electric connection is thus obtained between the different components which constitute the device according to the invention.
According to another feature, the electric power source is also arranged in the rigid receptacle.
According to another feature of the invention, the flexible body includes in succession a flexible reinforcing layer forming the bottom of the electronic device, in which is arranged the receptacle intended to accommodate the electronic unit and the electric power source, a flexible printed circuit having a bottom face and a top face respectively turned towards the reinforcing layer and towards the top of the electronic device, the electronic unit and the electric power source being secured to the bottom face of the flexible printed circuit, while the display cell is arranged on the top face of said flexible printed circuit, and a flexible protective layer covering the flexible printed circuit.
Thus, the present invention has the form of a strip of very small thickness at one location on the length of which there is an overthickness forming a rigid cavity in the volume of which are housed the fragile electronic components. The entire length of the strip can thus be used for the display of information or decorative patterns which may change if required.